A NEW BROAD-SPECTRUM SUNSCREEN 77 inhibitory effect of sunscreens on the amount of prostaglandin E 2 released from irra- diated skin, the flank skin of guinea pigs was treated with PUVA with or without the prior application of MDC-boehmite at 6% concentration. Released amounts of prosta- glandin E 2 significantly increased after PUVA treatment with 2.25 MED dose and reached three times the level in nonexposed areas. The prior application of MDC- boehmite complex markedly suppresses the release of prostaglandin E 2 up to the nonex- posed level in all mixture ratios (Figure 11). In the same PUVA treatment, the prior application of MDC-boehmite (1/1) + Parsol MCX (UVB sunscreen) with several combinations also markedly suppressed the release of prostaglandin E 2 up to the nonexposed level except in the absence of MDC-boehmite, which shows no release or weak inhibition of release (Figure 12). PREVENTIVE EFFECT OF MDC-BOEHMITE COMPLEX ON PROSTAGLANDIN E 2 RELEASE INDUCED BY UVB The flank skin of guinea pigs was irradiated by UVB at the 2 MED dose with or without the prior application of MDC-boehmite at the 6% concentration. Released amounts of prostaglandin E 2 significantly increase after UVB irradiation and reach 2.5 times the level of nonexposed areas. Prior application of MDC-boehmite complex mark- edly suppresses the release of prostaglandin E 2 up to the nonexposed level in all mixture ratios (Figure 13). (n•/•ml) U¾ 6-0 6-2 6-6 6-10 •-12 C U¾ 6-0 6-2 6-6 6-10 6-12 C MI)C/Bo•hmite % MI)C/Boehmlte % 2 hr poeUrradlaUon 24 hr posUrradiation Figure 11. Effect of MDC-boehmite complex (MDC 6%, boehmite 0-12%) on prostaglandin release in the medium of organ-cultured skin after exposure to PUVA. Hartley white guinea pigs received 4.2 mg/kg body weight of 8-methoxypsoralen in 30% ethanol intraperitoneally. Thirty minutes after administration, they were exposed to UVA of 3.5 mW/cm 2, emitted from Toshiba FL20BLB lamps. The samples, con- sisting of MDC-boehmite aqueous solution, were treated (2 mg/cm 2) ten minutes before irradiation. Irra- diated or nonirradiated skin was cut off at indicated hours postirradiation to assay the PGE 2 release in the medium of the organ culture. n = 3.

78 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS I'GE2 (ng/2ml) UV 2% 4% 6% 8% 10% Cont MDC/Boehmioee (1/1) Figure 12. Effect of MDC-boehmite (1/1) combined with P-MCX on prostaglandins released in the me- dium of organ-cultured skin after exposure to PUVA. Hartley white guinea pigs received 4.2 mg/kg body weight of 8-methoxypsoralen in 30% ethanol intraperitoneally. Thirty minutes after administration, they were exposed to UVA of 3.5 mW/cm 2, emitted from Toshiba FL20BLB lamps. The samples of W/O-type emulsion containing MDC-boehmite (1/1) and P-MCX were treated (2 mg/cm 2) ten minutes before irra- diation. Irradiated or nonirradiated skin was cut off at indicated hours postirradiation to assay the PGE 2 release in the medium of the organ culture. n = 3. 35 30 25 2O PGE2 (ng/2ml) 15 10 UV 0.0 0-2 0-6 0-10 0-12 C UV 6-0 6-2 6-6 6-10 6-12 C MDC/Boehmlte % MDC/Boehmite % 2 hr postirradiation 24 hr postirradiation Figure 13. Effect of MDC-bochmitc complex (MDC 6%, bochmitc 0-12%) on prostaglandins released in the medium of organ-cultured skin after exposure to UVB. Shaved back skin of Hartlcy white guinea pigs was treated with samples consisting of MDC-bochmitc aqueous solution and ten minutes later irradiated for 16 minutes with UVB using Toshiba FL20SE30 lamps at an intensity of 0.6 mW/cm 2. The samples were treated ten minutes before irradiation. Irradiated or nonirradiated skin was cut off at indicated hours postirradiation to assay the PGE 2 release in the medium of the organ culture. n = 3.